The repeated expulsion of exhaust gas from an engine may cause pulsed rapid movement of the gas through one or more exhaust pipes and out of one or more tail pipes. The pulsed rapid movement may create compression waves and objectionable noise, vibration and harshness (NVH). Exhaust mufflers have been used to reduce the noise. They typically serve to damp the noise, and/or to bounce the compression waves against partitions inside the muffler to create wave interference patterns to reduce the overall amplitude of the waves. Mufflers typically have an elongated oval shape, and an inlet at one longitudinal end and an outlet at the opposite end.
Tubing length and muffler volume can both help reduce noise. However, both parameters are often constrained by package limitations, especially in modern vehicles. At the same time, modern boosting techniques push more mass flow through the engine and exhaust system, potentially increasing exhaust noise.
One effort to reduce the proportion of space occupied by the vehicle muffler and exhaust tubing is disclosed in U.S. Pat. No. 4,760,894 to Harwood et al. Harwood discloses an exhaust muffler configured to accommodate a greater proportion of the available space on the vehicle. Harwood's approach recognizes a greater availability of transverse pockets of space available under the vehicle, which can require large bend tubing. To avoid large bend radius tubing, Harwood proposes a muffler with an internal configuration such that the exhaust pipe, or the tailpipe, may enter the muffler at an angle with the longitudinal axis of the muffler.
The inventors herein have recognized a number of problems with this approach. For example, the approach disclosed proposes a muffler having a substantially monolithic shape, and the resulting exhaust configuration still does not make significantly efficient use of the pockets of space under the vehicle.
Embodiments in accordance with the present disclosure may provide a conformal transverse muffler including an enclosure shaped to fit around a bottom and a side of a spare tire well of a vehicle. The enclosure may include a mid section fittable below the spare tire well, and two side sections fittable in opposite locations only radially outside of a circumference of the spare tire well. The side sections may be thicker than the mid section and may have a vertical center above a vertical center of the mid section. In this way, the available space under the vehicle may be effectively used by conforming the muffler shape to available space, thus enabling increased muffler volume within available packaging, such as for boosted engines. Further, in one example, this positioning and shaping of the muffler enables increased size of the vehicle trunk.
In one example, internal tubing may be coupled within a conformal muffler, such as described herein, and span transversely across the width to enable longer exhaust tailpipe lengths due to the wider lengths accommodated, thus meeting noise targets while also addressing backpressure issues. Such an approach is especially beneficial with dual exhaust tailpipes, since both may traverse the muffler's width in opposite directions to reduce package requirements.
Still another potential advantage is that the muffler may operate as an aerodynamic shield on the bottom of the vehicle due to its relative position under the spare tire, thus enabling improved fuel economy without requiring an additional shield, if desired.
Note that the conformal muffler may apply to single exhaust pipe systems, dual exhaust pipe systems, or systems having more exhaust pipes, as well as combinations thereof. For example, the conformal muffler may have a single exhaust inlet and a single exhaust outlet, multiple exhaust inlets and a single exhaust outlet, a single exhaust inlet and multiple exhaust outlets, duel inlets and duel outlets, or still further variations.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.
FIGS. 2-13 are drawn approximately to scale, although other relative dimensions may be used.